The specific biological process a compound uses to produce its effects — which receptor it targets, what signal it triggers, what happens downstream.A well-characterized MOA provides a mechanistic basis for predicting efficacy, selectivity, and potential off-target effects. MOA alone does not establish clinical efficacy — it is the hypothesis that clinical trials test. Many compounds with compelling MOA data in cell culture and animal models fail Phase II/III trials because the mechanism does not translate cleanly to the complex physiology of human disease. On this site, MOA is documented carefully as part of each compound’s evidence profile, with explicit distinction between MOA evidence and clinical efficacy evidence.